> >1. Emacs -Q
> >
> >2. open en elisp file. for example edebug.el
> >
> >3. Press left mouse button and select a region. Before to release left
> >mouse button press ALT. While keepeng ALT pressed release mouse button
> >
> >Result: a region is selected, and it cannot be unsected.
> >
> >This is a bug or an feature of emacs unknown by me?
>
> I think it is secondary selection. See also (info "(emacs) Secondary
> Selection").
>
>
You are right. Thanks.
However, there is surely a bug. Since you press the Meta key
only before releasing mouse-1, the event is slightly different from
pressing the Meta key before pressing mouse-1: in the former
case the first event is `down-mouse-1', and in the latter the
first event is `M-down-mouse-1'. Although the outcome is the
event `M-drag-mouse-1' in both cases, `mouse-drag-secondary'
seems not to get executed and other secondary selection
relating commands, such as `mouse-yank-secondary' fails to be
executed.